Test unresolved dependency analysis in the Gradle plugin

See gh-12784

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/resources/org/springframework/boot/gradle/plugin/SpringBootPluginIntegrationTests-unresolvedDependenciesAreAnalyzedWhenDependencyResolutionFails.gradle

@@ -0,0 +1,16 @@
+buildscript {
+	dependencies {
+		classpath files(pluginClasspath.split(','))
+	}
+}
+
+apply plugin: 'org.springframework.boot'
+apply plugin: 'java'
+
+repositories {
+	flatDir { dirs 'libs' }
+}
+
+dependencies {
+	compile 'org.springframework.boot:spring-boot-starter'
+}